A typical passenger conveyor, such as an escalator or a moving walk, includes a truss, a treadplate assembly driven through a loop by a machine, and a pair of balustrades extending along opposite sides of the treadplate assembly. Each balustrade includes a moving handrail that travels at the same speed as the treadplate assembly and enhances the safety and comfort of the passengers riding the conveyor.
The handrails are formed from a length of non-metallic material that is spliced together to form an endless band. The handrails are typically driven by a handrail drive assembly that is connected to the same machine that drives the treadplate assembly. Each handrail is tensioned over the outer edges of the balustrade in order to provide sufficient friction for the operation of the handrail drive assembly. Tension carriers, usually steel wire, are embedded in the handrail to accommodate the tension forces on the handrail.
Failure of the tension carriers may lead to an unacceptable operating condition. If the handrail stretches, the handrail drive assembly may not be able to drive the handrail at the same speed as the treadplate assembly, thus leading to discomfort of the passengers. If the handrail breaks, the handrail drive assembly will only drive the handrail until the point of the break reaches the handrail drive assembly. This will stop the handrail and leave the outer edge of the balustrade exposed.
Handrail monitoring devices have been used to determine if a failure has occurred in the handrail. These devices typically include a roller mounted on a resilient arm that is urged against the handrail. If a break has occurred, the resilient arm will move and actuate a switch to trigger the conveyor to stop. In addition, the speed of the handrail may be monitored through the rotation of the roller and if the measured speed varies from a predetermined speed, the conveyor may be shut down. A limitation of these types of devices, however, is that they wear over time and this wear may lead to improper operation and unnecessary stopping of the conveyor. In addition, any breaks in the handrail will not be detected until the location of the break reaches the monitoring device. At that point, most of the handrail may have been pulled off of the conveyor.
The above art notwithstanding, scientists and engineers under the direction of Applicant's Assignee are working to develop devices that effectively monitor the operational condition of conveyor handrails and are responsive to indications of degradation in the handrail.